POS1162 EVALUATION OF THE 2022 ACR/EULAR CLASSIFICATION CRITERIA FOR GPA AND MPA IN A EUROPEAN ANCA-ASSOCIATED VASCULITIS (AAV) COHORT
Authors: S. Krämer, T. Rauen, K. Pruin, T. Anslinger, M. Busch, T. Schmitt, R. Bergner, S. Mosberger, T. Neumann
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> In 2022, the ACR and the EULAR proposed new classification criteria for granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) based on numerical item scoring for different manifestations in ANCA-associated vasculitis (AAV). Recently, a low concordance rate of only 73% in comparison with the 2012 revised International Chapel Hill Consensus Conference Nomenclature and the 2007 European Medicines Agency (EMA) algorithm [1] was reported in a Korean cohort of 65 GPA patients. <h3>Objectives</h3> We performed a retrospective classification according to the new 2022 classification criteria of patients from our multi-centric AAV cohort, using a computational algorithm that involved existing clinical, laboratory and histological entries. These results were compared to prior clinical diagnoses. <h3>Methods</h3> Data of AAV patients from four tertiary referral centers (Germany and Switzerland) were collected between 2000 and 2021. The 2022 ACR/EULAR criteria for GPA and MPA were applied by algorithmically analyzing (1) BVAS entries for organ manifestation, (2) laboratory results for ANCA/ ELISA testing and (3) histological data for detection of granuloma and/or pauci-immune glomerulo-nephritis. Twenty cases with inconclusive ANCA status were excluded from computed analysis. Results were compared to previously reported diagnoses; whereby renal limited disease was considered a distinct entity. <h3>Results</h3> The final dataset included 305 cases, 294 (96.4%) of Caucasian ethnicity, 161 males (52.8%), median age 61 years (IQR 50-70). Based on the 2022 ACR/EULAR criteria, 299 (98%) cases could be unambiguously categorized, 180 patients were classified as GPA and 119 as MPA (<b>Table 1</b>). Positive concordance, i.e. patients matching the novel classification criteria and clinical diagnosis, was higher in MPA than in GPA patients (98.8 vs. 90.8%). By contrast, negative concordance, i.e. proportion of cases negative for both clinical and novel classification-based diagnosis, was higher in GPA (97.3 vs. 84.1%). Twenty-seven cases of renal limited disease were mostly reclassified as MPA (92%). Taken together, alignment of matching both, positive and negative cases in relation to all cases was 93.1% in GPA and 88.2% in MPA. Six cases (2%) that were clinically diagnosed as GPA could not be classified due to competing findings of increased eosinophil cell count and anti-proteinase-3 positivity. <h3>Conclusion</h3> In the present multi-centric cohort, our computational algorithm applying the novel 2022 ACR/EULAR criteria based on existing clinical, laboratory and histological data performed well to categorize 98% of all cases. Our findings demonstrated overall positive and negative concordance rates above 88% and suggest a higher specificity for GPA, but higher sensitivity for MPA classification criteria. <h3>Reference</h3> [1]Pyo JY, Ahn SS, Song JJ, <i>et al.</i> Reclassification of previously diagnosed GPA patients using the 2022 ACR/EULAR classification criteria. <i>Rheumatology (Oxford</i>) Published Online First: 4 May 2022. doi:10.1093/RHEUMATOLOGY/KEAC267 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Stefan Krämer: None declared, Thomas Rauen Consultant of: Vifor, Kristian Pruin: None declared, Teresa Anslinger: None declared, Martin Busch: None declared, Tobias Schmitt: None declared, Raoul Bergner Speakers bureau: Abbvie, Bristol Myers Squibb, Chugai, Glaxo Smith Kline, Galapagos, MSD, Novartis, Consultant of: Galapagos, Vifor, Sebastian Mosberger: None declared, Thomas Neumann Speakers bureau: Roche Pharma (Suisse) AG, GlaxoSmithKline AG, Celgene Switzerland, UCB-Pharma AG, Janssen-Cilag AG, Vifor Pharma Switzerland, Novartis Switzerland, Consultant of: Roche Pharma (Suisse) AG, GlaxoSmithKline AG, Celgene Switzerland, AstraZeneca GmbH, Janssen-Cilag AG, Amgen Switzerland AG, Vifor Pharma Switzerland, Grant/research support from: Vifor Pharma Switzerland.